HDRMerge does not produce any looks. Well, everything has a look - I mean that making the image look one way or another is not HDRMerge’s goal. HDRMerge creates a raw file which can store a high dynamic range, but it requires further tone-mapping and processing.
Hugin has several dynamic range-related options, I’m not sure which one you used. One of them is to enfuse the bracketed images. Unlike HDRMerge, enfuse skips the high dynamic range step and goes straight to tone-mapping, using the best-exposed pixel in the final image. It too requires further processing, but not tone-mapping.
Hugin also has an option to create a HDR in the (Open)EXR and TIFF formats, but I have not tried that option. If it does what the label implies it does, then it should result in a file capable of storing a high dynamic range, but unlike the output of HDRMerge this file will not require demosaicing (the source images must already have been demosaiced).
When dealing with HDR files using libre software, one generally tone-maps them using Luminance HDR.